Used oil furnaces are similar to standard oil burning furnaces, but have been adapted to handle oil products that have been previously used in a traditional lubricating operation, such as used crankcase oil up to 50 SAE, used transmission fluid, and even #2, #4 and #5 fuel oils. Such oil products can have significantly varying viscosities and significantly varying burning characteristics, as well. Typically, used oil products are collected into a tank to be supplied to the furnace from a single source.
The burner nozzle combines a flow of compressed air with the flow of preheated used oil to atomize the used oil and inject a stream of compressed air and atomized used oil droplets into the combustion chamber of the furnace where it is ignited to create a flame and provide a heat source. Known used oil furnace burner nozzles utilize an in-line burner nozzle configuration coupled directly to the front door of the multi oil furnace.
The structural configuration of the furnace is important in the efficiency of the operation of the furnace. A flame target at the end of the combustion chamber opposite the burner nozzle is provided to contain the flame created within the combustion chamber. An exit for the exhaust gases, sometimes referred to flue gases or combustion gases, is typically provide for exhaust of the combustion gases from the combustion chamber. The combustion gases are directed out of the furnace for discharge to the atmosphere. Known furnace configurations utilize conduits to redirect the combustion gases through a serpentine path to the side of the combustion chamber before discharging the gases from the furnace. The serpentine path allows ventilation air to be moved around the conduits to absorb heat therefrom before being discharged into the ambient atmosphere where heating is desired.
Another furnace configuration is disclosed in U.S. Pat. No. 5,531,212, granted to Benjamin K. Smoker, et al., on Jul. 2, 1996, in which the combustion gases are directed through horizontally disposed upper and lower banks of exhaust conduits oriented parallel to and around the combustion chamber. The combustion gases are directed through an outlet at the rear of the combustion chamber into the upper bank of horizontal conduits which is connected to a header at the front end of the combustion chamber and then directed into the lower bank of conduits, which are connected to an exhaust header that directs the combustion gases through a discharge opening and away from the furnace.
In U.S. Pat. No. 6,694,968 granted to Jacob Dienner, et al, on Feb. 24, 2004, the exhaust tubes are arranged in a horizontal circular pattern at the end of the combustion chamber in a manner that the exhaust tubes are spaced apart and connected to a rear header that directs the combustion gases to a pair of opposing discharge openings for discharge of the combustion gases from the furnace. Ventilation air is blown into the furnace housing by a blower mounted at the rear of the furnace housing to direct the ventilation air through a central annular opening in the rear header to exit the rear header in the center of the circular array of exhaust tubes. The ventilation air then passes around the exhaust tubes that then around the combustion chamber to be discharged at the front of the furnace housing into the room in which the furnace is supported. A major disadvantage of the used oil furnace configuration disclosed in U.S. Pat. No. 6,694,968 is the required length of the furnace housing required to contain the combustion chamber and the exhaust conduit array behind the combustion chamber.
A different exhaust conduit configuration is found in U.S. Pat. No. 5,363,836 granted on Nov. 15, 1994, to Eugene C. Briggs in which the exhaust gases are directed from the rear of the combustion chamber into a flat header located within the furnace housing above the combustion chamber. Ventilation air is blown from the rear of the furnace housing to mover around the flat header and around the combustion chamber before being discharged into the room through discharge openings at the front of the furnace housing. A more compact furnace housing is disclosed in U.S. Pat. No. 4,955,359 granted on Sep. 11, 1990, to Eugene C. Briggs, et al., in which the combustion gases are collect from the rear off the combustion chamber into a vertically oriented exhaust header around which ventilation air is passed to collect heat therefrom before passing around the combustion chamber and exiting the discharge openings at the front of the furnace housing.
A vertical array of exhaust tubes is disclosed in U.S. Pat. No. 2,737,173, issued to Roy C. Hauck, et al., on Mar. 6, 1956. The Hauck exhaust conduits are oriented above the combustion chamber and collect combustion gases directly from an opening at the top of the combustion chamber. The Hauck combustion gases pass through the vertical array of exhaust conduits that direct the combustion gases into a horizontally disposed discharge opening. Ventilation air is passed around the vertical exhaust conduits and around the combustion chamber by a fan and then discharged into the ambient air around the furnace.
It would also be desirable to provide a used oil furnace configuration that provides a compact configuration that efficiently directs ventilation air around the exhaust conduits and around the combustion chamber to collect heat therefrom before being discharged into the room in which the furnace is mounting.